Survey: Mac OS hit record 7.57% in Jan.; Windows lost a little ground

The news was almost lost yesterday in the Microhoo hoopla: even as Microsoft (MSFT) was trying to buy its way into some kind of parity with Google (GOOG) by gobbling up Yahoo (YHOO), a new survey showed that Apple (AAPL) had taken another little bite out of Redmond’s core business.

According to the latest market share data from Net Applications, Mac OS X’s slice of the computer operating system market grew 3.56% in January while Microsoft Windows’ dropped .36%.

As Net Applications measures it (more on its methodology below), the Mac’s market share stands at a record 7.57%, up 21.7% from Jan. 2007.

“Apple’s market share gains in December for the Mac and iPhone are impressive,” the report concludes. “However, for the last days of December, the numbers are nothing short of spectacular.”

The really good news for Apple, according to Net Applications, came in the last two days of the month, when Mac OS X hit 8.01%.

Windows is still dominates the desktop, of course, with a 91.46% share, but that’s down from 93.33% a year earlier.

Net Applications’ monthly surveys sample data from visitors to some 40,000 websites operated by the firm’s clients. As such, the findings are a snapshot of installed base rather than a month-to-month measure of computer systems sold. The January results are summarized in the table below. The full report can be viewed here.